1. Field of the Invention
The present invention relates to a desulfurizing and denitrating tower.
2. Description of Related Art
In a prior art desulfurizing and denitrating tower, a catalyst is contained in a moving bed, which has two louvers parallel to each other, so as to move in the moving bed from above toward below. A gas to be processed is supplied to the moving bed from one louver and is discharged through the other louver.
FIG. 2 is a sectional view of main parts of the prior art desulfurizing and denitrating tower.
As shown in FIG. 2, a moving bed 10 containing a catalyst 9 is formed by an inlet louver 11 and an outlet louver 12 disposed parallel to each other to surround the moving bed 10 from both sides. Two front and rear lower walls 13, 14 are extended downwardly obliquely from respective lower ends of the inlet louver 11 and the outlet louver 12. The spacing between the lower walls 13, 14 is gradually narrowed toward below, and a discharge port 16 for the catalyst 9 is formed at lower ends of the lower walls 13, 14.
A discharge roller 18 is provided in such a manner as to be partly located in the discharge port 16. The catalyst 9 supplied to an upper end of the moving bed 10 is moved gradually downwardly in the moving bed 10 upon rotation of the .discharge roller 18 so that the catalyst is discharged through the discharge port 16 at a constant rate. A deflecting cone 20 having an inverted-V shape in cross-section is disposed in a lower region of the moving bed 10 in opposite relation to the discharge port 16 for smoothing the downward movement of the catalyst 9.
On the other hand, a gas to be processed is supplied to the moving bed 10 through the inlet louver 11 and is desulfurized and denitrated while moving transversely, followed by being discharged through the outlet louver 12.
FIG. 3 is a schematic view of the prior art desulfurizing and denitrating tower.
In FIG. 3, a processed gas introduction port 34 and a processed gas discharge port 35 are formed respectively in opposite side walls 32, 33 of a tower body 31. An inner space of the tower body 31 is partitioned by the inlet louver 11 and the outlet louver 12 disposed parallel to each other with the moving bed 10 defined between the inlet louver 11 and the outlet louver 12.
In this tower, a gas to be processed enters the moving bed 10 from the processed gas introduction port 34 through the inlet louver 11. The processed gas is sufficiently contacted with the catalyst 9 (FIG. 2) in the moving bed 10, and then reaches the processed gas discharge port 35 after passing the outlet louver 12.
On the other hand, the catalyst 9 for desulfurizing and denitrating the processed gas is supplied to the moving bed 10 from a supply port 46 formed at an upper end of the tower body 31, and is moved downwardly in the moving bed 10 to reach the discharge port 16.
The discharge roller 18 is disposed in the discharge port 16 and is rotated at a predetermined speed so that the catalyst 9 in the moving bed 10 is moved downwardly at a predetermined moving speed and is then discharged through the discharge port 16.
The catalyst 9 discharged through the discharge port 16 is circulated to the supply port 46 through a line 61 with a regenerative unit (e.g., a sieving or screening unit) 60 disposed in the line 61.
In the prior art desulfurizing and denitrating tower described above, however, a distribution of the catalyst 9 supplied to the moving bed 10 in a pattern a is changed as represented by a pattern b while the catalyst is moving downwardly in the moving bed 10. Accordingly, a uniform flow of the catalyst 9 can not be created in the moving bed 10, and the moving speed of the catalyst 9 is lowered in the vicinity of the inlet louver 11. As a result, the catalyst 9 is loaded with dust contained in the processed gas in the vicinity of the inlet louver 11. Also, the catalyst 9 tends to stagnate in a boundary portion c between the inlet louver 11 and the lower wall 13, a boundary portion d between the outlet louver 12 and the lower wall 14, as well as an upper surface e of the deflecting cone 20. Furthermore, the desulfurization rate achieved by the catalyst 9 in the moving bed 10 cannot be increased and the processing cost is raised correspondingly.